Michael Ignatieff, the Member of Parliament for Etobicoke-Lakeshore and the Liberals’ deputy leader, has found the time in a hectic political season to write a thoughtful book-review essay on humanitarian intervention in The New Republic. In an election campaign in which, as usual, foreign policy is being neglected, this is especially welcome.

While the book he reviews, Freedom’s Battle, by Gary Bass, is a history of humanitarian intervention in the 19th and early 20th centuries, Mr. Ignatieff persuasively sets out the current state of affairs: “The demand for humanitarian intervention is high, but the supply is weak.”

More particularly, the suffering in Darfur, Georgia, Zimbabwe and Myanmar has recently evoked the idea of the responsibility to protect, which Mr. Ignatieff cautiously describes as “something approaching a principle of international law.”